let caidan=document.getElementById("caidan"); //找标签
let list=caidan.children;
for(let i=0 ;i <= list.length;i++){
	function show(){
		let smalllist=this.children[1]; //找到small-box
		if(!smalllist){
			return null;
		} //判断二级菜单是否存在
		smalllist.classList.add("menuShow");
	}
	list[i].addEventListener("mouseenter",show);  //鼠标靠近出现二级菜单
	function leave(){
		let smalllist=this.children[1];
		if(!smalllist){
			return null;
		}
		smalllist.classList.remove("menuShow");
		
	}
	list[i].addEventListener("mouseleave",leave);//鼠标离开二级菜单消失
}